The electrical-system voltage in most conventional vehicles amounts to 14V. In hybrid vehicles or vehicles having an electrical drive, however, voltages that may rise to several hundred volts are used. Voltages higher than 60 Volts are referred to as “high voltages”.
For safety-related reasons, high-voltage vehicle electrical systems must be able to be switched off and discharged. Known high-voltage vehicle electrical systems include an active discharge device for this purpose. This device is usually made up of a two-pole main switch for cutting the battery off from the rest of the vehicle electrical system, and also a switchable resistor, via which the charge is able to be reduced. As an alternative, a passive discharge device may be used as well. This device is generally made up of at least one resistor, which is connected in parallel with the energy store and the high-voltage vehicle electrical system. One disadvantage of the known switch-off and discharge device is that the resistor must have a very large size relative to its capacity and thus requires relatively much space if discharge times of less than five seconds are to be realized. The discharge time that is achievable with the aid of such a known switch-off and discharge device is usually at least 60 seconds and thus quite long.